1. **Stating the problem:** We want to evaluate the integral $$\int \frac{-2}{2x^2 - x^3 - x} \, dx$$.
2. **Simplify the denominator:** Factor the denominator:
$$2x^2 - x^3 - x = -x (x - 1)^2$$
3. **Rewrite the integral:** Using the factorization, the integral becomes:
$$\int \frac{-2}{-x (x - 1)^2} \, dx = \int \frac{2}{x (x - 1)^2} \, dx$$
4. **Partial fraction decomposition:** We express:
$$\frac{2}{x (x - 1)^2} = \frac{A}{x} + \frac{B}{x - 1} + \frac{C}{(x - 1)^2}$$
Multiply both sides by the denominator $x (x - 1)^2$:
$$2 = A (x - 1)^2 + B x (x - 1) + C x$$
Expand:
$$2 = A (x^2 - 2x + 1) + B (x^2 - x) + C x$$
$$= (A + B) x^2 + (-2A - B + C) x + A$$
5. **Equate coefficients:** For the polynomial identity to hold for all $x$:
- Coefficient of $x^2$: $A + B = 0$
- Coefficient of $x$: $-2A - B + C = 0$
- Constant term: $A = 2$
6. **Solve the system:**
From $A = 2$, substitute into $A + B = 0$:
$$2 + B = 0 \implies B = -2$$
Substitute $A$ and $B$ into $-2A - B + C = 0$:
$$-2(2) - (-2) + C = 0 \implies -4 + 2 + C = 0 \implies C = 2$$
7. **Rewrite the integral with partial fractions:**
$$\int \frac{2}{x} \, dx + \int \frac{-2}{x - 1} \, dx + \int \frac{2}{(x - 1)^2} \, dx$$
8. **Integrate each term:**
- $$\int \frac{2}{x} \, dx = 2 \ln|x| + C_1$$
- $$\int \frac{-2}{x - 1} \, dx = -2 \ln|x - 1| + C_2$$
- $$\int \frac{2}{(x - 1)^2} \, dx = 2 \int (x - 1)^{-2} \, dx = 2 \cdot \frac{(x - 1)^{-1}}{-1} + C_3 = -\frac{2}{x - 1} + C_3$$
9. **Combine results:**
$$\int \frac{-2}{2x^2 - x^3 - x} \, dx = 2 \ln|x| - 2 \ln|x - 1| - \frac{2}{x - 1} + C$$
10. **Simplify logarithms:**
$$2 \ln|x| - 2 \ln|x - 1| = 2 \ln \left| \frac{x}{x - 1} \right|$$
**Final answer:**
$$\boxed{\int \frac{-2}{2x^2 - x^3 - x} \, dx = 2 \ln \left| \frac{x}{x - 1} \right| - \frac{2}{x - 1} + C}$$
where $C$ is an arbitrary constant of integration.
Integral Partial Fractions 2E126C
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.